I would say, for the most part, phone interviews are out of the question. Siley1, I was in your shoes--I applied all over the country but nowhere near where I was living.
Go and talk to your professors that you will be taking next semester before this semester even ends. Let them know that you will have multiple interviews that will require you to miss class on several occasions (explaining to them it is for advanced education--they will most likely be ok with that and help you accomodate).
Besides, your interviews are going to be in the beginning of the semester ( nobody really learns anything in undergrad until first test/midterm anyway) and your interviews will fall on a Thursday or Friday (there may be some exceptions), so you are only likely to miss at most one class period for all of your classes per week when you are out of town.
As for the cost of treking yourself all over...no advice I can give can help you there. It adds up--believe me. But, I would rather see the school where I would potentially be going before I made my decision about it.
